[O] Error on opening org files

[Richard Stanton]

I just updated org-mode to version 7.8.09 (release_7.8.09.199.g5e4cff.dirty), 
and now get the following error when I try to open any .org file:

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
  org-babel-header-arg-expand()
  run-hook-with-args-until-success(org-babel-header-arg-expand)
  org-cycle((4))
  org-set-startup-visibility()
  org-mode()
  set-auto-mode-0(org-mode nil)
  set-auto-mode()
  normal-mode(t)
  after-find-file(nil t)
  find-file-noselect-1(#<buffer work.org> "c:/Dropbox/org/work.org" nil nil 
"c:/Dropbox/org/work.org" ((16640 12 . 1731) (37630 . 48608)))
  find-file-noselect("c:/Dropbox/org/work.org" nil nil nil)
  find-file("c:/Dropbox/org/work.org")
  steve-ido-choose-from-recentf()
  call-interactively(steve-ido-choose-from-recentf nil nil)